Comparison of smooth and hairy attachment pads in insects: friction, adhesion and mechanisms for direction-dependence.

Adhesive pads on the legs of animals can be classified as either 'smooth' or 'hairy' (fibrillar). It has been proposed that the hairy design conveys superior and controllable adhesion. However, no study has yet compared the basic performance of both systems.

Biomechanics of smooth adhesive pads in insects: influence of tarsal secretion on attachment performance.

Many insects possess smooth adhesive pads on their legs, which adhere by thin films of a two-phasic secretion. To understand the function of such fluid-based adhesive systems, we simultaneously measured adhesion, friction and contact area in single pads of stick insects (Carausius morosus). Shear stress was largely independent of normal force and increased with velocity, seemingly consistent with the viscosity-effect of a continuous fluid film.